Effects of very high loads on fatigue life of NR elastomer materials

This article provides detailed investigations into the fatigue behavior of natural rubber. Very important aspects of this, like Mullins-effects, strain crystallization, crack nucleation at flaws and crack growth, are examined in detail and used to explain experimental results. In addition to SEM micrograph investigations of the fracture surfaces, new aspects of fatigue fracture of rubber can be explained and well-known explanations can be confirmed. It is shown, that the global crack growth in the direction of the crack front is caused by interactions of several cracks growing in alternating directions. Results from strain-controlled experiments show that Woehler curves also are valid in regions of very high loads. Further experiments, using a spectrum of two different amplitudes each, clarify that Miner’s rule also is valid for damage accumulation when the load spectrum contains few excessively high loads.